AP_Math: add rotateXY
AP_AHRS: use rotateXY for speed

Saves 0.1ms at 100hz
Copter: Failsafe GCS typo in comments

replaced GPS by GCS word in different comments locations
Copter Motors: replace limit bitmask with structure
Copter: remove unused earth frame rate controllers
LeadFilter: removed this unused library

This was used to project the GPS position forward to compensate for lag
but this has become unnecessary with the introduction of the inertial
nav in x and y axis.
Plane: move failsafe variables into a structure

this makes the logic a bit easier to follow
Plane: don't read control switch when ch3 is in failsafe

use ch3_counter not just the final flag
Plane: check the control switch a bit more often

faster response to mode changes
Plane: set mode CIRCLE on short failsafe in AUTO

this makes the code match the docs
AP_Math: added two new vector/matrix ops for kalman airspeed filter
AP_GPS: added velocity_vector() method
Plane: added note on type of airspeed in docs
AP_Airspeed: added auto-calibration support

This uses a Kalman filter to calculate the right ARSPD_RATIO at runtime

Pair-Programmed-With: Paul Riseborough <p_riseborough@live.com.au>
Plane: use new airspeed calibration code

Pair-Programmed-With: Paul Riseborough <p_riseborough@live.com.au>
Plane: update to new license boilerplate for GPLv3

we had LGPLv2 in some places, despite the fw being GPLv3
AP_Airspeed: added EAS2TAS in airspeed driver

this keeps the true airspeed ratio in the airspeed driver, which seems
the most logical place
AP_AHRS: added true airspeed support in AHRS

use true airspeed for wind calculations, and allow other drivers to
ask for the current ratio
AP_TECS: use ahrs EAS2TAS for true airspeed
Plane: updates for new EAS2TAS scaling